SiC (silicon carbide) is expected to be a next-generation material for semiconductor devices. SiC has excellent physical properties with the band gap being threefold, the breakdown electric field strength being about tenfold and the thermal conductivity being about threefold as compared to Si (silicon). By taking advantage of these properties, a semiconductor device, which has a high breakdown voltage and a low loss and is capable of being operated at a high temperature, can be provided.
Semiconductor rectifying devices are classified roughly into PIN diodes using a p-n junction between a p-type semiconductor and a n-type semiconductor, and Schottky barrier diodes (SBD) using a Schottky junction between a semiconductor and a metal. The Schottky barrier diode is a unipolar device having only majority carriers as carriers, and is therefore suitable for operations in a high frequency range as compared to the PIN diode.
A device structure has been proposed in which a leak current at the off-time is reduced by depleting a drift layer using a Schottky barrier height of a Schottky barrier diode. For increasing the width of the depletion layer, it is required to form a high barrier between a semiconductor and a metal.